Add link checking and fix broken documentation references

[Copilot]

Documentation contained broken external URLs and malformed internal references. External links pointed to deprecated/moved resources; internal links used .md extensions instead of .html generated by docfx.

Changes

Automated Link Checking

• Added .github/workflows/check-links.yml using lychee
• Runs on PRs with markdown changes, weekly schedule, and manual dispatch
• Creates issues for detected broken links

External Link Fixes

• CredHub API (14 occurrences): credhub-api.cfapps.io → github.com/cloudfoundry/credhub/blob/main/docs/
• Spring AMQP (2 occurrences): Removed /html/ from reference path
• Spring Cloud (8 occurrences): projects.spring.io/spring-cloud → spring.io/projects/spring-cloud-*
• Steeltoe Samples: Updated to main branch path

Internal Link Fixes

• Converted 30+ internal documentation links from .md to .html extension
• Affected files in docs/articles/ and docs/guides/ directories

Example fix:

- [Steeltoe Messaging](/docs/v3/messaging/index.md)
+ [Steeltoe Messaging](/docs/v3/messaging/index.html)

Note

74 soft-broken docs.pivotal.io links remain (redirect to generic pages). Require VMware/Broadcom documentation mapping research.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• credhub-api.cfapps.io
  • Triggering command: /usr/bin/curl curl -I -L REDACTED (dns block)
• docs.cloudfoundry.org
  • Triggering command: /usr/bin/curl curl -I -L REDACTED (dns block)
• docs.spring.io
  • Triggering command: /usr/bin/curl curl -I -L REDACTED (dns block)
  • Triggering command: /usr/bin/curl curl -I REDACTED (dns block)
• spring.io
  • Triggering command: /usr/bin/curl curl -I REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Scan for broken links to external URLs</issue_title>
<issue_description>We should run a tool that recursively follows all the links and reports which ones are broken. And then correct or remove them.

For example, there are many links pointing to docs.pivotal.io, such as https://docs.pivotal.io/spring-cloud-services/1-5/common/circuit-breaker/, which today redirects to the generic Broadcom page at https://techdocs.broadcom.com/us/en/vmware-tanzu.html.</issue_description>

Comments on the Issue (you are @copilot in this section)

@bart-vmware Remaining _hard_ broken links after the fixes in #385 are listed in the table below. Note this does not include soft broken links, such as the one mentioned above.

URL	Anchor Text	Linked From
https://credhub-api.cfapps.io/	CredHub API	[https...</comment_new>

• Fixes Scan for broken links to external URLs #375

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